A pioneering farming project using field management techniques dating back to the 13th century has transformed a stretch of coast into a haven for endangered animals, birds, insects and wildflowers.

The experimental return to “strip-field farming” close to the spectacular Rhossili Bay on the Gower peninsula in south Wales is being credited with a threefold increase in the number of species of wildflowers and the appearance of rare birds such as the hen harrier and grasshopper warbler.

As many as 63 butterflies were spotted in 60 seconds in one of the strip fields at the Vile, compared with a maximum of six in neighbouring pastures that are farmed conventionally.

The Vile, which is old English for strip fields, was farmed in the old-fashioned way until the late 1940s. Shortages then led to the intensification of agriculture across the UK including, to a more limited extent, the Vile.

The National Trust, which owns around three-quarters of the 111 acre site, launched a project to wholly restore the strip fields two years ago. Rangers and 80 volunteers have created 2,000 metres of banks and hedges that had been removed to satisfy the demands of heavily mechanised farming, turning six fields into a patchwork of 17 different areas. The plots rejoice in names such as Bramble Bush, Sandyland and Priest Hay.

A flock of linnets feeds on linseed left after harvest at the Vile. Photograph: National Trust

The team has planted a variety of crops including oats, barley, millet and buckwheat, along with flowers such as poppies, lavender and lupins. The sunflower fields, which have wonderful views of the Worm’s Head promontory, have thrilled visitors and drawn huge numbers of bees and other insects.

Strip-field farming, also known as an open field system, was introduced during the medieval period as a way for villagers to share land. The field would have been owned by a landowner and the villagers would rent strips in which to grow their own crops.

The National Trust concedes that it is not for now an economically viable form of farming, but it hopes ways might be found to make it attractive to some farmers.

Alan Kearsley-Evans, the trust’s countryside manager, said: “It’s fantastic to see such results. We have simply reverted to farming sustainably and with astounding results.

“We know that our farm is very small, but the principle of what we’re doing and the results could be applied to large intensive farms. We aim to prove in a few years just how viable this method is and to showcase the many benefits it delivers.”

The strip-field farm has attracted at least 10 species of bee. Photograph: John Miller/National Trust

A key advantage of the strip-field system, and using banks to divide fields, is to help deflect the wind that can whip across the coastline. This not only protects the crops, but has also meant that returning wildlife such as the 21 varieties of butterfly and 10 species of bee can forage in the sheltered microclimate. Wind deflection also prevents moisture loss.

Mark Hipkin, a National Trust ranger, said: “By planting vast amounts of sunflowers, poppies and our other crops we have attracted more pollinators and birds. In fact, this year taking a walk through the sunflower fields we’ve seen a bumble bee on nearly every sunflower head.

“We aim to harvest next month in an old 1970s combine harvester which is small enough to turn in the restored narrow strip fields.”

The team plans to rotate the crops next year, allocate a further two or three of the strip fields to lavender and introduce bee hives to produce honey.

Among the flora and fauna that the Trust say have benefited are butterflies such as the small blue, grayling and wall brown.Twenty-three rare bird speciesand four types of threatened reptiles including adders, slow worms and toads, were also spotted.

Volunteer Sarah Oakey-Phillips said: “The Vile is now a living historical example of strip farming from times long ago. Working the land from the early barren stages … to a wildlife haven bursting in colour is what makes our work truly rewarding.”